TWI544282B - Illumination system of a microlithographic projection exposure apparatus - Google Patents

Description

Illumination system of lithographic projection exposure device

The present invention is generally directed to an illumination system for a lithographic projection exposure apparatus and to methods of operating the same.

Photolithography (also known as photolithography or simply lithography) is a technique used to fabricate integrated circuits, liquid crystal displays, and other microstructure devices. The lithography process along with the etch process is used to pattern features in a thin film stack that has been formed on a substrate such as a germanium wafer. At each layer of fabrication, the wafer is first coated with a photoresist (which is a material that is sensitive to light of a particular wavelength). Then, the wafer with the photoresist at the top is exposed to the projected light through a mask in the projection exposure apparatus. The mask contains a circuit pattern to be imaged on the photoresist. After exposure, the photoresist is developed to produce an image corresponding to the circuit pattern contained in the mask. The etch process then transfers the circuit pattern to the thin film stack on the wafer. Finally, remove the photoresist. This process is repeated with different masks to create multilayer microstructured components.

Projection exposure devices generally include an illumination system that illuminates a field on the mask that has, for example, a rectangular or curved slit. The device further includes: a masking table for aligning the mask, a projection objective (sometimes referred to as a "lens") for imaging the illuminated field on the mask to the photoresist, and for aligning A wafer alignment station for coating a photoresist wafer.

One of the important goals in the development of projection exposure devices is the ability to lithographically define structures that are getting smaller and smaller on the wafer. Small structures can result in high integration densities that generally have a beneficial effect on the performance of the microstructured components produced with the assistance of this device.

Various methods have been developed in the past to achieve this goal. A method has been used to reduce the wavelength of the projected light used to image the circuit pattern onto the photoresist. This is the fact that the minimum size of the features defined by the lithography is roughly proportional to the wavelength of the projected light. Therefore, manufacturers of such devices strive to use projected light having increasingly shorter wavelengths. The shortest wavelengths currently used are 248 nm, 193 nm, and 157 nm, thus falling within the deep (DUV) or vacuum (VUV) ultraviolet spectral range. The next generation of commercial devices will use projected light with even shorter wavelengths, about 13.5 nm, which is in the extreme ultraviolet (EUV) spectral range. The EUV device contains a mirror instead of a lens because the lens absorbs almost all of the EUV light.

Another method is to improve the illumination of the mask. Ideally, the illumination system of the projection exposure apparatus illuminates each point of the field illuminated by the mask using projection light having a well defined spatial and angular irradiance distribution. The term "angle irradiance distribution" is used to describe how all of the light energy of a beam of light (which is polymerized toward a particular point on the mask) is distributed among the various directions of the light that make up the beam.

The angular irradiance distribution of the projected light impinging on the mask is generally applicable to the type of pattern to be imaged onto the photoresist. For example, relatively large sized features may require different angular irradiance distributions compared to small sized features. The most commonly used angular irradiance distributions are conventional, toroidal, bipolar, and quadrupole illumination settings. These terms refer to the irradiance distribution in the surface of the illumination system. For example, at the annular illumination setting, only the annular region is illuminated on the surface of the crucible. Thus, only a small range of angles are present in the angular irradiance distribution of the projected light, and all of the light is obliquely illuminated onto the mask at a similar angle.

Different means are known in the art for modifying the angular irradiance distribution of the projected light on the mask plane to achieve the desired illumination setting. In order to achieve maximum elasticity of the irradiance distribution at different angles in the mask plane, it has been proposed to use a mirror array which determines the irradiance distribution in the surface of the crucible.

In the European patent EP 1 262 836 A1, the mirror array is realized as a micro-electromechanical system (MEMS) comprising more than 1000 microscopes. Each mirror can be tilted against two orthogonal tilt axes. Therefore, the radiation incident on the mirror device can be reflected to almost any desired hemispherical direction. A concentrating lens is arranged between the mirror array and the surface of the crucible, which converts the angle of reflection produced by the mirror to a position on the surface of the crucible. This illumination system makes it possible to illuminate the 瞳 surface with a plurality of points, each of which is associated with a particular mirror and is free to move around the 瞳 surface by tilting the mirror.

A similar illumination system using a mirror array is disclosed in the patent documents US 2006/0087634 A1, US 7061582 B2 and WO 2005/026843 A2.

Although the illumination system using the mirror array is very flexible for modifying the angular irradiance distribution, the uniformity of the spatial and angular irradiance distributions on the illumination field in the mask plane is still a problem. For future illumination systems, the field dependence of these quantities may need to be very low.

Methods have been developed to reduce the field dependent focus on an optical integrator, which is typically used in illumination systems to generate a plurality of secondary sources. The beam emitted by the secondary source is superimposed on a mask plane by a concentrator or on a field stop plane optically conjugated to the mask plane. An optical integrator typically includes an array of one or more optical grating elements that produce a beam of light associated with a secondary source. One or more optical grating elements dedicated to this beam form an optical channel that is independent of the other optical channels. Since each beam of light associated with the optical channel completely illuminates the mask or field stop plane, optical elements located within the optical channel can be used to adjust the illumination characteristics.

For example, U.S. Patent No. 5,615,047 describes a plate arranged before an optical integrator and includes a plurality of filter regions, each of which is associated with a single optical channel of an optical integrator. Since the position of the filter element is optically conjugate to the mask or field stop plane, the projection rate distribution of the filter region can be selected to obtain a uniform spatial irradiance distribution at the mask or field stop plane.

Furthermore, U.S. Patent No. 6,049,374 teaches the use of an absorbing filter element associated with a particular channel of an optical integrator.

U.S. Patent Publication No. US 2009/0021715 A1 describes an illumination system that removes residual field dependence of unwanted angular irradiance distributions. For this purpose, optical elements (e.g., helium) placed in individual optical channels change certain optical characteristics of the beams associated with these optical channels.

However, there is still a need for modifications to the illumination system, particularly with respect to the field irradiance distribution of the incident illuminance of the incident mask.

Accordingly, it is an object of embodiments of the present invention to provide an illumination system that increases the resiliency associated with the field dependence of the angular irradiance distribution at the mask level.

According to an embodiment of the invention, this object is achieved by an illumination system comprising an optical integrator comprising an array of optical grating elements, wherein the beam is associated with each optical grating element. The illumination system further includes a concentrator that superimposes the light beams associated with the optical grating elements on a common field plane, the common field plane being the same or optically conjugated to a mask plane, and one of the illuminations to be illuminated during operation of the illumination system Set to the mask plane. The modulator of the illumination system is configured to adjust a field of irradiance distribution at one of the angles in a field that is illuminated by the illumination system in the mask plane. The modulator includes a plurality of modulator units, wherein each modulator unit is associated with at least one of the beams (preferably only one) and is disposed at a position prior to the concentrator such that only the associated beam is incident Modulator unit. In addition, each modulator unit is configured to variably redistribute a spatial and/or angular irradiance distribution of the associated beam without blocking any light. The illumination system further includes a control device configured to control the modulator unit by: if the control device receives an input command that the field dependence of the angular irradiance distribution in the mask plane needs to be adjusted, At least one modulator unit redistributes a spatial and/or angular irradiance distribution of an associated beam.

Thus, embodiments of the present invention discard conventional methods that attempt to produce the same well-defined angular irradiance distribution at each point of the illumination field on the mask plane (ie, reduce the field dependence of the angular irradiance distribution to a very small tolerable value) . Rather, embodiments of the present invention are directed to providing an illumination system that enables an operator of the apparatus to quickly change the field dependence of the angular irradiance distribution on the mask plane. This makes it possible to selectively illuminate different parts of the illumination field with different angular irradiance distributions. If these distributions are specific to the circuit pattern illuminated in these sections, the pattern will be more correctly transferred to a photoresist or other type of light-sensitive surface.

However, the present invention can also be used in applications where it is not necessary to illuminate different portions of the mask with different illumination settings. The ability to quickly adjust the field dependence of the angular irradiance distribution of the mask level can then be used to effectively reduce field dependence, even if the field dependence changes over time and therefore cannot be arranged in the optical channel of the optical integrator. The fixed optics are used to reduce the case.

In a specific embodiment, the modulator configuration is such that a first angular irradiance distribution is generated in a first portion of the illumination field and a second angular irradiance distribution different from the first angular irradiance distribution is derived from The second part of the field.

In particular, in a scanner type device in which the mask moves in a scanning direction during photoresist exposure, the first and second portions may be formed by lines extending in the scanning direction. The first portion may abut one end of the illumination field and the second portion may abut one of the opposite ends of the illumination field. In the case of a scanner type device, the one end and the opposite end may define an illumination field in one of the vertical scanning directions.

In other embodiments, the first portion is a two-dimensional region in which the first angular irradiance distribution is uniform, and the second portion is a two-dimensional region in which the second angular irradiance distribution is uniform.

If the device is of the scanner type, the illumination field typically has a long dimension along one of the X directions and a short dimension along the Y direction, wherein the Y direction is perpendicular to the X direction and corresponds to the scanning direction of the device. Next, the first portion has at least one Y coordinate identical to the second portion, but no X coordinate. In other words, the two portions are arranged side by side in the X direction or may be displaced in the Y direction, but do not have a common point falling on one of the lines extending in the parallel Y direction.

In some embodiments, it is even possible to quickly change the angular irradiance distribution such that the angular irradiance distribution changes as the mask is projected onto the photosensitive layer during the scanning operation. Then, the first and second portions formed by the two-dimensional regions may be arranged in the scanning direction Y in tandem such that the two portions may also have a common X coordinate.

In general, the first and second angular irradiance distributions of the two portions may be related to an illumination setting selected from the group consisting of: conventional illumination settings, angular illumination settings, bipolar illumination settings, n 4 n pole illumination setting.

In other embodiments, each of the modulator units is arranged in a grating field plane that is positioned in front of the array of optical grating elements in a direction of light propagation. Each modulator unit is configured to variably redistribute the spatial irradiance distribution of the associated beam in the grating field plane without blocking any light.

This takes advantage of the fact that the grating field plane is optically conjugate with the common field plane, so any spatial redistribution of the associated beam in the grating field plane is directly converted to a spatial irradiance distribution that is redistributed in the common field plane. Since each modulator unit is associated with a particular beam of light that is propagating in a direction determined by the position of the associated optical grating element toward a common field plane, if the modulator unit changes by the associated beam in the common field plane The spatial irradiance distribution produced will change the field dependence of the angular irradiance distribution.

In general, the grating field planes associated with optical grating elements are coplanar. However, if the optical grating elements have different optical properties, the grating field plane can also be displaced or tilted along the optical axis.

In some embodiments, each of the modulator units is configured to move in a direction in the plane of the grating field along a direction of the optical axis of the vertical illumination system, the region being associated with the beam of the modulator unit Irradiated. The illumination field in the common field plane is also moved, the amount of movement being proportional to the amount by which the area in the raster field plane is moved. In a scanning type device, the moving direction may be equal to the X direction. In this context, it should be noted that the grating field plane is usually not a plane in the mathematical sense, but an optical definition, and thus may have a certain "thickness". Therefore, the tilting movement in such a "thick" field plane is still considered to be the movement of the vertical optical axis.

The movement of the illuminated area can be achieved by the modulator unit without changing the angular irradiance distribution of the associated beam. The angular irradiance distribution produced by the particular beam in the common field plane is then determined only by the position of the associated optical grating element, but is substantially independent of the position of the illumination area in the grating field plane associated with the beam. .

To configure a modulator unit to be able to variably redistribute the spatial irradiance distribution of the associated beam in the grating field plane typically requires a certain amount of space in the grating field plane to accommodate the optical components, the brakes, And other mechanical components required for this purpose. This means that the illuminated portion of the grating field plane must be separated by slits.

An optical integrator that produces a grating field plane (where the illumination portion is separated by a slit) may comprise a first array of optical grating elements, a second array, and a third array in a direction of light propagation Wherein the grating field plane is between the second array and the third array of optical grating elements. Such an optical integrator is described in German Patent Application No. DE 10 2009 045 219, filed on Sep. 30, 2009.

In other embodiments, each of the modulator units is arranged in or adjacent to a plane of the pupil that lies behind the array of optical grating elements in the direction of light propagation. Each modulator unit is configured to variably redistribute the angular irradiance distribution of the associated beam in the pupil plane without blocking any light. This takes advantage of the fact that the angular irradiance distribution in the pupil plane is converted to a spatial irradiance distribution in a common field plane, where the common field plane is Fourier related to the pupil plane.

In this context, each modulator can be configured to tilt a beam associated with the modulator unit for a tilt axis that is perpendicular to the optical axis. This will result in a movement of the spatial irradiance distribution in the common field plane.

In the case of a scanning device, the tilt axis can be equal to the Y direction, which is equal to the scan direction.

Regardless of the location of the modulator unit, each modulator unit can include an optical component configured to vary the direction of propagation of the associated beam incident thereon. Additionally, each modulator unit can include a brake coupled to the optical component and configured to change the position and/or orientation of the optical component in response to receiving a control signal from one of the control devices.

In this paper, the parallel movement of the beam is also considered a change in the direction of propagation.

The optical element can be a refractive optical element, in particular a lens, a cymbal or a Fresnel, or a diffractive optical element.

Generally, the brake is configurable to displace the optical element in a direction that is oblique to (preferably perpendicular to) one of the optical axes of the illumination system.

In other embodiments, the brake system is configured to rotate the optical element about a rotational axis that is oblique (preferably perpendicular) to one of the optical axes of the illumination system.

In some embodiments, the modulator configuration is such that the angular irradiance distribution varies discontinuously across the illumination field. This would be particularly useful if the illuminated mask contains different pattern areas, each pattern area requiring a uniform but different angular irradiance distribution.

In other embodiments, the modulator configuration is such that the angular irradiance distribution varies continuously over at least a portion of the illumination field. This may be advantageous, for example, if the density, size, and/or orientation of the pattern features are not uniform over a large pattern area, but vary in at least a portion of the illumination field in a substantially continuous manner.

In the latter case, the first portion may be a first line in which the first angular irradiance distribution is uniform. The second portion may be a second line in which the second angle irradiance is evenly distributed. Next, the modulator system is configured such that the first angular irradiance distribution is continuously converted to the second angular irradiance distribution in a region disposed between the first line and the second line.

To continuously produce a varying irradiance distribution, a modulator unit can be used that is configured to vary an irradiance distribution in a region of the grating field plane illuminated by the beam associated with the modulator unit, Without moving it. In other words, the size, geometry, and location of the illuminated area in the raster field plane are not altered by the modulator unit, but the irradiance distribution in this area changes in response to receiving a control signal from one of the control devices.

In the case of a continuously varying angular irradiance distribution, each modulator unit is configurable to convert the irradiance distribution from a uniform irradiance distribution to a modified irradiance distribution that increases linearly or decreases along a reference direction. . In the case of a scanning device, this direction may be equal to the X direction, which is the vertical scanning direction Y.

Another aspect of an embodiment of the present invention is a method for operating a lithographic projection exposure apparatus, comprising the steps of:

(a) providing a lithographic projection exposure apparatus comprising an illumination system and a projection objective;

(b) providing a mask that will be illuminated by the illumination system;

(c) defining one of the required first angular irradiance distributions and one of the required second angular irradiance distributions different from the first angular irradiance distribution;

(d) illuminating the mask by obtaining a first angular irradiance distribution at a first portion of the mask and a second angular irradiance distribution at a second portion of the mask different from the first portion .

The first and second angular irradiance distributions are related to illumination settings selected from the group consisting of: conventional illumination settings, angular illumination settings, bipolar illumination settings, n 4 n pole illumination setting.

The first portion may be a two-dimensional region in which the first angular irradiance is uniformly distributed. The second portion may also be a two-dimensional region in which the second angular irradiance is uniformly distributed. The feature pattern contained in the mask may be different in the first portion than in the second portion.

Alternatively, the first portion may be a first angle illuminance distribution uniform to the first line, and the second portion is a second angle irradiance distribution uniform to the second line. Next, the first angular irradiance distribution is continuously converted to the second angular irradiance distribution in a region arranged between the first line and the second line.

The method can include the step of controlling the modulators included in the illumination system in a manner that achieves first and second angular irradiance distributions.

The method can also include the step of redistributing a spatial and/or angular irradiance distribution associated with the beam of optical grating elements contained in the illumination system without blocking any light.

The angular irradiance distribution can be varied when the mask is projected by the projection objective onto a light-sensitive surface.

Embodiments of the invention are also generally applicable to EUV illumination systems in which the optical grating elements are mirrors.

definition:

The term "field plane" is used herein to mean a plane that is optically conjugate to the plane of the mask.

The term "瞳 plane" is used herein to mean a plane that intersects the edge rays passing through different points in the plane of the mask.

The term "even" is used herein to mean a position-independent property.

The term "light" is used herein to mean any electromagnetic radiation, particularly visible light, UV, DUV, VUV, EUV light and X-rays.

The term "light ray" is used herein to mean light whose propagation path can be described by a line.

The term "light bundle" is used herein to mean a plurality of rays of light having a common origin in the field plane.

The term "light beam" is used herein to mean light that passes through a particular lens or other optical component.

The term "orientation" is used herein to mean the angular alignment of an object in three dimensions. The orientation is usually represented by a set of three angles.

The term "location" is used herein to refer to the location of a reference point for an object in three-dimensional space. The position is usually represented by a set of three Cartesian coordinates. Thus, the orientation and position are a complete description of the configuration of an object in three dimensions.

The term "optical grating element" is used herein to mean any optical element, such as a lens, iridium, or diffractive optical element, that is arranged with other optical grating elements to create or maintain a plurality of optical channels in close proximity.

"The optical integrator" as used in this system indicates an increase NA‧ a product of an optical system, wherein NA is the numerical aperture, and a is an exposure field region.

The term "concentrator" is used herein to mean an optical element or an optical system that establishes (at least approximately) a Fourier relationship between two planes, such as a field plane and a pupil plane.

The term "conjugate plane" is used herein to mean a plane in which an imaging relationship is established. More information on the concept of conjugate planes has been revealed in E. Delano's paper entitled "First-Level Design and y ," Chart (First-order Design and the y , Diagram), published in Applied Optics, 1963, Vol. 2, No. 12, pp. 1251-1256.

The term "field dependence" is used herein to mean any functional dependence of a physical quantity on a position in a plane.

The term "spatial irradiance distribution" is used herein to mean how the overall irradiance varies over the actual or virtual surface on which the light is incident. The spatial irradiance distribution is typically described by the function I _s (x, y) , where x , y are the spatial coordinates of the points on the surface. If applied to the field plane, the spatial irradiance distribution needs to integrate the irradiance produced by the plurality of beams.

The term "angle irradiance distribution" is used herein to mean how the irradiance of a beam varies with the angle of the light constituting the beam. The angular irradiance distribution is generally described by a function I _a (α, β) , where α, β are angular coordinates that describe the direction of the light. If the angular irradiance distribution has field dependence, I _a will also be a function of the field coordinates, ie I _a = I _a (α, β, x , y ).

I. General structure of projection exposure device

1 is a perspective and highly simplified view of a projection exposure apparatus 10 in accordance with the present invention. Device 10 includes an illumination system 12 that produces a projected beam of light. The illumination system 12 illuminates the field 14 on the mask 16, which includes a pattern 18 formed by a plurality of small features 19, indicated schematically by the thin lines in FIG. In this particular embodiment, the illumination field 14 has a ring segment shape that does not include the optical axis OA of the device. However, other shapes of illumination fields 14, such as rectangles, are also contemplated.

Projection objective 20 images pattern 18 within illumination field 14 on a photosensitive layer 22 (e.g., photoresist) supported by substrate 24. The substrate 24 formed of the germanium wafer is arranged on a wafer stage (not shown) such that the top surface of the light sensing layer 22 is exactly located in an image plane of the projection objective 20. The mask 16 is disposed in the object plane of the projection objective 20 by a masking station (not shown). Since the magnification β of the projection objective 20 is |β|<1, the reduced image 18' of the pattern 18 in the illumination field 14 is projected onto the photosensitive layer 22.

During projection, the mask 16 and the substrate 24 are moved in a scanning direction corresponding to the Y direction indicated by FIG. The illumination field 14 then scans the entire mask 16 such that the patterned area larger than the illumination field 14 can be continuously imaged. The speed ratio of the substrate 24 and the mask 16 is equal to the magnification β of the projection objective 20. If the projection objective 20 reverses the image (β < 0), the mask 16 and the substrate 24 move in opposite directions, as indicated by arrows A1 and A2 in FIG. However, the present invention is also applicable to a stepper tool in which the mask 16 and the substrate 24 are not moved during the projection of the mask.

II. Multiple illumination settings

2 is an enlarged perspective view of the mask 16. The pattern 18 on this mask contains three identical first pattern regions 181a, 181b, 181c which are arranged one after the other in the Y direction. For the sake of simplicity, it is assumed that the feature 19 of the first pattern regions 181a, 181b, 181c is a straight line extending in the Y direction. The pattern 18 further includes three identical second pattern regions 182a, 182b, 182c which are also arranged one after the other in the Y direction, but are laterally displaced from the first pattern regions 181a, 181b, 181c such that the first pattern region 181a The 181b, 181c and the second pattern areas 182a, 182b, 182c have no common X coordinate. It is assumed that the second pattern regions 182a, 182b, 182c include features 19 extending in the X direction and features 19 extending in the Y direction.

The mask 16 shown in Figure 2 is assumed to be used in a fabrication step in which two different dies are simultaneously exposed and will undergo the same subsequent fabrication steps, such as etching. The grain system is sufficiently small to be adjacent to each other within the image field of the projection objective 20 having a width W in the X direction, as shown in FIG. Three first type dies associated with the first pattern regions 181a, 181b, 181c and three second type dies associated with the second pattern regions 182a, 182b, 182c may be exposed during a complete scan period. Next, the scanning direction is reversed or the mask 16 is returned to its home position without any illumination, and the next scanning cycle is performed. In this method, two columns of different grains on the substrate 24 can be simultaneously exposed.

In general, different patterns require different angular irradiance distributions at the mask level if optimal imaging quality is desired. In this particular embodiment, it is assumed that features 19 extending in the Y direction are optimally imaged onto the photosensitive layer 22 with X bipolar illumination settings. In Fig. 2, the dashed circle indicates a meander 26 which is associated with a beam of light that is concentrated toward a field point located in one of the first pattern regions. In the crucible 26, two poles 27 spaced apart from each other in the X direction represent the direction in which light travels toward the field point. Since the pattern is assumed to be uniform on the first pattern regions 181a, 181b, 181c, it is necessary to generate this X dipole illumination setting at each of the first pattern regions 181a, 181b, 181c.

The second pattern regions 182a, 182b, 182c associated with the second type of grains include features extending in the X direction and features 19 extending in the Y direction. For these features 19, it is assumed that the annular illumination setting has the best imaging quality. 2 illustrates a ring 28 that is illuminated in the crucible 26, wherein the crucible 26 is associated with a beam of light that is concentrated toward a field point at one of the second pattern regions 182a, 182b, 182c. Likewise, this annular illumination setting will result from each of the second pattern regions 182a, 182b, 182c.

This means that the illumination system 12 must be capable of simultaneously generating two different illumination settings that are placed side by side within the illumination field 14. Hereinafter, the structure of the illumination system 12 capable of performing this task will be described in more detail with reference to FIGS. 3 through 13.

III. General structure of the illumination system

3 is a cross-sectional view of the illumination system 12 shown in FIG. For the sake of clarity, the illustration of FIG. 3 is rather simplified and not to scale. This means in particular that different optical units are represented by only one or very few optical elements. In fact, these units can contain more lenses and other optical components.

The illumination system 12 includes a housing 29 and a light source 30. In the particular embodiment shown, the source 30 is implemented as a quasi-molecular laser. Light source 30 emits projected light having a wavelength of about 193 nm. Other types of light sources 30 and other wavelengths are also contemplated, such as 248 nm or 157 nm.

In the particular embodiment shown, the projected light emitted by source 30 enters beam expanding unit 32 where the beam expands. For example, beam expansion unit 32 can include a plurality of lenses or can be implemented as a mirror arrangement. The projected light from the beam expanding unit 32 is formed as an almost collimated projected beam 34.

Next, the projected beam 34 enters a 瞳 definition unit 36 for producing a variable spatial irradiance distribution in a subsequent pupil plane. For this purpose, the 瞳 definition unit 36 comprises an array 38 of microscopic mirrors 40 that can individually tilt the two orthogonal axes with the aid of a brake. 4 is a perspective view of array 38 depicting how two parallel beams 42, 44 are reflected to different directions depending on the angle of inclination of mirror 40 into which beams 42, 44 are incident. In Figures 3 and 4, array 38 contains only 6x6 mirrors 40; in practice, array 38 can include hundreds, even thousands, of mirrors 40.

The 瞳 definition unit 36 further includes a crucible 46 having a first planar surface 48a and a second planar surface 48b that are oblique to the optical axis OA of the illumination system 12. At these inclined surfaces 48a, 48b, the incident light is reflected by total internal reflection. The first surface 48a reflects the incident light toward the mirror 40 of the mirror array 38, while the second surface 48b directs the light reflected from the mirror 40 to the exit surface 49 of the crucible 46. Thus, the angular irradiance distribution of light emerging from the exit surface 49 can be varied by individually tilting the mirror 40 of the array 38. Further details regarding the 瞳 definition unit 36 can be found in U.S. Patent Publication No. US 2009/0116093 A1.

With the aid of the first concentrator 50, the angular irradiance distribution produced by the 瞳 definition unit 36 is converted to a spatial irradiance distribution, wherein the first concentrator 50 directs the incident light to the optical integrator 52. In this particular embodiment, optical integrator 52 includes a first array 54a of optical grating elements 56, a second array 54b, and a third array 54c.

Figure 5 is a perspective view of three arrays 54a, 54b, 54c. Each array includes a sub-array of optical grating elements 56 on the front and back sides of the support plate, wherein the sub-arrays are produced by parallel cylindrical lenses extending in the X or Y direction. The use of a cylindrical lens is generally particularly advantageous where the refractive power of the optical grating element 56 should be different along X and in the Y direction.

Figures 6 and 7 show a top view of array 54a and a cross-sectional view taken along line VII-VII, respectively, in accordance with an alternate embodiment. The optical grating element 56 herein is formed from a plano-convex lens having a square outline. The other arrays 54b, 54c have only the convex surface of the optical grating element 56 having a different curvature than the array 54a.

Referring again to FIG. 3, the optical grating elements 56 of the first, second and third arrays 54a, 54b, and 54c are arranged one after the other such that one optical grating element 56 of each array is directly associated with One of the other two arrays of optical grating elements 56. The three optical grating elements associated with each other are aligned along a common axis and define an optical channel. Within optical integrator 52, the light beams propagating in one optical channel are not staggered or overlapped with the light beams propagating in other optical channels. In other words, the plurality of optical channels associated with the optical grating elements 56 are optically isolated from one another.

The grating field plane 58 is disposed between the second array 54b and the third array 54c, and the modulator unit 60 of the modulator 62 is disposed therein. The modulator unit 60 is coupled to the control device 66 via a control line 64, which is then coupled to a central device control 68 that controls the overall operation of the projection exposure device 10.

In this particular embodiment, the pupil plane 70 of the illumination system 12 is disposed after the third array 54c (which may also be disposed before). The second concentrator 72 establishes a Fourier relationship between the pupil plane 70 and the field stop plane 71, and the adjustable field stop 74 is arranged in the field stop plane 71. The field stop plane 71 and the grating field plane 58 in which the modulator unit 60 is arranged are optically conjugate.

This means that the regions in the grating field plane 58 in the optical channel are imaged on the field stop plane 71 by the associated optical grating elements 56 and second concentrators 72 of the third array 54c. The image of the illuminated area within the optical channel is superimposed in the field stop plane 71 and this causes a very uniform illumination of the field stop plane 71. This procedure is generally described by identifying the illuminated areas in the optical channels with secondary light sources that collectively illuminate the field stop plane 71.

The field stop plane 71 is imaged on the mask plane 78 by the field stop objective 76, wherein the mask 16 is arranged with the aid of a mask stage (not shown). The adjustable field stop 74 is also imaged on the mask plane 78 and defines at least the short sides of the illumination field 14 that extend in the scan direction Y.

IV. Modulator

The function of the modulator 62 will be explained hereinafter with reference to FIG. 8, which is a schematic longitudinal cross-sectional view of three adjacent optical channels I, II and III formed in the optical integrator 52. The projected light of the incident optical integrator 52 has low divergence. For the sake of simplicity, this divergence will be ignored in this discussion, so the light incident on the first array 54a of optical grating elements 56 is assumed to be collimated. Further assume that the three optical grating elements 56 of the optical integrator 52 are uniformly illuminated, as indicated by arrow A3 of FIG. For the sake of simplicity, the optical grating elements 56 formed at the intersection of orthogonal cylindrical lenses are represented as lenticular lenses.

The optical grating elements 56 of the first two arrays 54a, 54b have the effect that the width of the beam associated with the individual optical channels I, II, and III is reduced in the X direction. The reduction may also occur in the Y direction, but may have different reduction factors. The area illuminated on the modulator unit 60 has a rectangular shape and is separated by a slit at least in the X direction, wherein the slit is represented by a blank area between the adjacent arrow pair A4 in FIG.

The modulator unit 60 has the effect that these illumination regions in the grating field plane 58 move laterally in the X direction. This lateral movement is indicated by the arrow pair A5 of optical channels II and III in FIG. In the above optical channel I, the modulator unit 60 is in a neutral state such that the irradiance distribution does not move.

The optical grating elements 56 and the second concentrator 72 of the third array 54c image the irradiance distribution in the grating field plane 58 onto the field stop plane 71, as already mentioned above. The irradiance distribution in the field stop plane 71 produced only by the optical channel I above is indicated by a solid line in FIG. This irradiance distribution is concentrated in the field stop plane 71 because the modulator unit 60 has no moving irradiance distribution on its entry side.

However, the irradiance distribution in the field pupil plane 71 produced by the intermediate and lower optical channels II and III (which are shown in dashed lines and dotted lines, respectively) is now laterally shifted in the X direction. This is only the result of an optical conjugation between the grating field plane 58 and the field stop plane 71 in each optical channel.

The angular irradiance distribution produced by each of the optical channels I, II, and III in the field stop plane 71 depends on the position of the optical channels in the pupil plane 70. The greater the distance between the optical axis of the second concentrator 72 and the position of the optical channel, the greater the angle of illumination produced by the optical channel. Thus, the three optical channels I, II, and III are capable of producing different illumination fields with different angular irradiance distributions.

This will be explained in more detail below with reference to FIGS. 9 and 10. 9 is a top plan view of a grating field plane 58 of optical integrator 52 in which only 3x3 optical channels are provided. The dark areas in Figure 9 represent the areas in the grating field plane 58 illuminated by the projected light. As can be seen in Figure 9, in operation of the modulator unit 60 associated with the individual optical channels, the five regions 80 move along -X and the two regions 81 move in the +X direction. The two regions 82 are not illuminated, i.e., the pupil definition unit 36 does not direct any light to the optical grating elements 56 associated with these regions 82.

As explained above, the lateral movement of the region 80 shown in FIG. 9 also causes the illumination region in the field stop plane 71 and the movement of the mask plane 78. By appropriately selecting the size of the region 80, it can be achieved that the left or right half of the field 14 on the mask 16 is illuminated by the individual optical channels.

Figure 10 is a perspective view of the mask 16 and describes the illumination conditions of this simplified example. It can be seen that at the half of the illumination field 14, an angular irradiance distribution similar to the C-quad illumination setting (which includes five poles, namely four outer poles 83a and one center pole 83b) can be obtained. These five poles correspond to the five illumination areas 80 shown in FIG.

On the other half of field 14, an angular irradiance distribution similar to the Y bipolar illumination setting of two poles 84 can be obtained. These two poles 84 correspond to the two illumination areas 81 shown in FIG.

It will be apparent from the foregoing that if the number of optical channels is sufficient, almost any arbitrary illumination can be placed over the two halves of the illumination field 14, so that the 瞳 definition unit 36 can also produce the desired on the optical integrator 52. Irradiance distribution. In the following, two different embodiments of the modulator unit 60 will be described with reference to FIGS. 11 and 12.

In the particular embodiment illustrated in Figure 11, each modulator unit 60 of the modulator 62 includes two cylindrical lenses 86, 88 that are individually displaceable in the X direction, as shown by the double arrows in FIG. Show. By decoupling the cylindrical lenses 86, 88 from the optical axes of the individual optical channels, the beam of light associated with the optical channels is laterally displaced. This takes advantage of the fact that the effect of a decentered lens is the same as that of a centered lens plus a triangular ridge. To displace the cylindrical lenses 86, 88, the brakes designated 90, 92 are coupled to the cylindrical lenses 86, 88. The brakes 90, 92 change the position of the lenses 86, 88 in response to control signals received from the control device 66.

FIG. 12 shows a cross-sectional view of another embodiment of modulator 62. In this particular embodiment, each modulator unit 60 includes a crucible 94 that is shaped as a parallelepiped. Each turn 94 has two pairs of planar rectangular surfaces and a pair of planar surfaces having a parallelogram profile. With the aid of a brake designated 96, the cymbal 94 is rotatable about the axis of rotation 98.

In the rotational position of the upper optical channel I shown, the 稜鏡94 is in a neutral state in which the beam is incident perpendicularly through the two planar surfaces. In the rotational positions of the intermediate and lower optical channels II and III shown, the beam passes through two inclined planar surfaces such that the beam is moved laterally.

13 is a schematic longitudinal cross-sectional view of one of the optical channels of optical integrator 52. In this illustration, the ray trajectories of the center beam 100 and the edge beam 102 are indicated by solid lines and broken lines, respectively. The focal lengths of the optical grating elements 56 of the three arrays 54a, 54b, and 54c are labeled f _a , f _b , and f _c . The shaded area 104 in the raster field plane 58 indicates that no projected light will pass through one of the spaces and thus can be used to accommodate components such as the brakes, support structures, or the shaft of the modulator unit 60.

The irradiance distribution on the optical grating element 56 having the first array 54a of diameter d is imaged on the grating field plane 58 at a reduced scale of d'/d, wherein the grating field plane 58 has a diameter d'. As can be seen from the slits between the planes of focus, the optical grating elements 56 are arranged in a slightly defocused manner. For example, this is enabled to adjust for telecentricity errors. For a more detailed description of the optical integrator 52, reference is made to the German patent application DE 10 2009 045 219, filed on Sep. 30, 2009.

V. Alternative embodiment

14 is a schematic cross-sectional view of illumination system 112 in accordance with another embodiment, similar to FIG. In this particular embodiment, optical integrator 152 includes only two arrays 154a, 154b of optical grating elements 156. However, the main difference from the illumination system 12 shown in FIG. 3 is that the modulator 162 including the modulator unit 160 is not arranged in the grating field plane 58, but is arranged in the pupil plane 70, and the pupil plane 70 is fastened. After being connected to the last array of optical grating elements 156, between second array 154b and second concentrator 72. In addition, the modulator unit 160 is configured to variably redistribute the angular irradiance distribution (non-spatial irradiance distribution) of the associated beam in the pupil plane 70 without blocking any light.

A more detailed explanation will be made below with reference to Fig. 15, which is similar to Fig. 8 showing three adjacent optical channels I, II and III of optical integrator 152.

The modulator unit 160 is arranged at a position after the second array 154b, and the light beams associated with the optical channels I, II and III of the optical integrator 152 have not overlapped here. Thus, the light system incident on each modulator unit 160 is only related to one of the optical channels I, II, and III. As previously mentioned, the modulator unit 160 is an angular irradiance distribution that modulates the associated beam, as can be clearly seen by comparing arrows A7 and A6, which are indicated after and before the modulator unit 160, respectively. The light of the relevant beam. The second concentrator 72 converts the different angular irradiance distributions into different spatial irradiance distributions in the field stop plane 71.

In the above optical channel I, the modulator unit 160 is in an operational state in which the divergence of the beam is increased. Thus, the spatial irradiance distribution depicted in solid scale 106 in field stop plane 71 has the largest dimension along the X direction.

In the intermediate optical channel II, the modulator unit 160 is in an operational state in which the divergence is not increased, but the beam associated with this optical channel is tilted in the -X direction. This resulting spatial irradiance distribution is indicated by dashed line 108 in FIG. The width of the spatial irradiance distribution in the X direction is half the maximum width produced by the upper optical channel I, and the irradiance level is twice as high as the irradiance level produced by the optical channel I above.

In the lower optical channel III, the modulator unit 160 is in an operational state in which the beam of light associated with the optical channel is tilted in the +X direction. This resulting spatial irradiance distribution is indicated by dashed line 110 in FIG.

Therefore, by tilting the light beam associated with the modulator unit 160 against a tilt axis (which is parallel to the Y axis and thus the optical axis OA of the vertical illumination system 112), it is possible to illuminate the field stop plane 71 with a particular optical channel again. Different parts of the mask 16. If the modulator channel unit 160 of the optical channel above is configured such that the divergence does not increase in the neutral operating state, the modulator 162 will have the same effect as the modulator 62 shown in FIG.

Figure 16 is a schematic longitudinal cross-sectional view of three optical integrators 152 and modulators 160 in close proximity to optical channels I, II and III. Each modulator unit 160 includes a triangular bore 113 and a brake (not shown), wherein the brake is configured to be displaced 稜鏡 113 in the +X or -X direction in response to a control signal received from the control device 66. . In the neutral position of the crucible 113, which is shown as the modulator unit 160 associated with the optical channel I above, the divergence increases, but the beam as a whole is not tilted. If the brake is operated and the 稜鏡113 is laterally displaced in the -X or +X direction (which is shown as two modulator units 160 associated with the intermediate optical channel II and the lower optical channel III), then these optical channels are associated The beam of light is tilted in the Y direction, as previously described with reference to FIG.

If the position of the 稜鏡 113 is between the center position of the optical channel I above and the one of the end positions of the optical channels II and III shown in the middle and below, the field pupil plane 71 will be present. A graded irradiance distribution with two non-zero irradiance levels is obtained. The ratio between the two stages depends on the X position of 稜鏡113. Thus, each optical channel can direct any portion of the light to two portions of the illumination field in the field stop plane 71.

In this particular embodiment, it is also advantageous to have free space available between the optical channels I, II and III for receiving the brakes for displacing the crucible 113. This can be achieved by appropriately designing the optical integrator 152.

Figure 17 is a cross-sectional view of the crucible 113' in the XZ plane in accordance with an alternative embodiment. The 稜鏡 113' of this embodiment is the "fresnelized" equivalent of the triangular 稜鏡 113 shown in FIG. Therefore, Fresnel 113' does not have a substantially triangular cross section, but has a zigzag stepped profile as shown in FIG. Fresnel 稜鏡 113' may have the advantage of the aberration generated by the triangular 稜鏡 113 shown in FIG.

If the 稜鏡113 or 113' cannot be displaced in the X direction, for example because there is no space available to enable the movement of the 稜鏡113, 113', or to accommodate the brakes and support structures or other mechanical components, The other refracting optical elements displaced in the Y direction are replaced to adjust the angular irradiance distribution of the beam associated therewith.

Figure 18 is a perspective view of a refractive optical element, generally designated 116. The optical element 116 includes two refractive wedges 118, 120 arranged side by side, wherein one of the wedges 118 is positioned by aligning the wedge 118 from the position of the other wedge 120 to a rotational axis (which is parallel to the Z direction). Obtained by rotating 180°. If the refractive optical element 116 is used in the modulator unit 160 shown in Figure 16 such that it can be displaced in the Y direction, the wedge 118 or wedge 120 may be completely exposed to the individual, as long as the size is properly determined. The beam of the optical channel. Next, the same effect as the optical channel II and the lower optical channel III shown in FIG. 16 is achieved. If the refractive optical element 116 is located at a half of the beam passing through the wedge 118 and the other half of the beam passing through the center of the wedge 120, the same effect as the upper optical channel I shown in FIG. 16 can be substantially achieved.

VI. Irradiance management

In the foregoing, the problem of how the available amount of projected light needs to be distributed over various optical channels to achieve the desired irradiance and angular light distribution on the mask plane is not discussed.

In the following, how the irradiance management needs to be performed is to be performed for the different pattern areas 181a, 181b, 181c and 182a, 182b, 182c to achieve the illumination setting shown in Fig. 2.

For the sake of simplicity, it will be assumed that the number of optical channels available in the optical integrator is 6x6. Fig. 19 schematically shows how the irradiance distribution (hereinafter referred to as the 瞳 irradiance distribution) in the 瞳 26 associated with the individual field points in this case must vary in the X direction on the illumination field 14. In the left half of the illumination field 14, the illumination setting 122 should be annular, and the right half of the illumination field 14 should be set to the X dipole illumination setting 124. In the representation of Figure 19, the two different illumination settings are approximately approximated as a result of the limited number of available optical channels.

Further assume that in the case of the circular illumination setting 122, all of the areas illuminated in the crucible are twice as large as in the case of the X bipolar setting. Since the point on the mask 16 should receive the same amount of light, whether it is in the left or right half of the illumination field 14, the irradiance in the illuminated area is set in the ring illumination if compared to the X bipolar illumination setting. The next need is half. This is illustrated in regions 126, 127 in Figure 19, which are related to different optical channels of optical integrator 152 and have different degrees of blackening.

These radon irradiance distributions, which differ from the field points in the left and right halves of the illumination field 14, are generated by optical integrator 152 and modulator 162. Figure 20 depicts the irradiance distribution in the pupil plane 70 of the illumination system 112 required for this purpose. It can be seen that there are four different irradiance levels, namely zero level 128 (white), one third irradiance level 130 (light gray), two thirds irradiance level 132 (dark gray), and full irradiance. Level 134 (black).

The highest irradiance level 134 is required for those optical channels that need to direct light to the two halves of the illumination field 14. More specifically, these optical channels require one-third of the available light to be directed to the left half of the illumination field 14 (the annular illumination setting should be generated therein), and the remaining two-thirds of the available light must be directed to the right half of the illumination field. (X bipolar illumination setting should be generated). The fractional irradiance distribution in this field pupil plane 71 or mask plane 78 can be obtained, for example, from 稜鏡113 or 113', where 稜鏡113 or 113' is located in the center of optical channel I shown in Figures 15 and 16. The position is shown between the intermediate optical channel II and the end position of the lower optical channel III.

Two-thirds of the irradiance level 132 is required for those optical channels that direct light only to the right half of the illumination field 14 to obtain an X-bipolar illumination setting 124. As previously mentioned, the irradiance needs to be twice as large as the area where the light is directed only to the left half of the illumination field 14 (where the annular illumination setting 122 is obtained). In these areas, one third of the irradiance level 130 is required.

The zero irradiance level 128 is required to completely direct light to those areas of the pupil plane 70 of the illumination field 14.

With the aid of the mirror array 38 of the 瞳 definition unit 36, four different irradiance levels 128, 130, 134, 132 can be easily achieved. For simplicity, if it is assumed that array 38 (only) contains 36 mirrors each producing the same irradiance, then three mirrors 40 can direct the projected light to each optical channel of the full irradiance level 134, and the two mirrors 40 can The projected light is directed to each optical channel requiring two-thirds of the irradiance level 132, and a mirror 40 directs the projected light to each of the optical channels requiring one-third of the irradiance level 130. All 36 mirror systems have four mirrors that do not have any light directed to the optical integrator 52.

However, in general, the mirror does not produce the same irradiance as previously assumed, but rather a rather different (although known) irradiance. Next, the mirror 40 that produces the highest irradiance can be controlled to direct the projected light to those areas that require full irradiance level 134. A mirror 40 that produces approximately two-thirds of the full level 134 is controlled to direct the projected light to the area requiring two-thirds of the irradiance level 132, and so on.

VII. Continuous changes in angular irradiance distribution

In the foregoing, it has been assumed that two portions of the mask 16 are arranged side by side in the X direction, which are illuminated at different angular irradiance distributions. However, it is also conceivable to illuminate the mask 16 in such a way that the angular irradiance distribution is continuously varied, and in particular in the direction of the vertical scanning direction Y.

Figure 21 depicts how the 瞳 irradiance distribution can vary in the X direction within the illumination field 14, which is similar to the representation of Figure 19. At the left end of the illumination field 14, an annular illumination setting 122 is produced. At the right end of the illumination field 14, an X dipole illumination setting 124 is generated. The different gray scales within the turns between the opposite ends indicate how the angular irradiance distribution continuously varies between the ends of the illumination field 14.

Thus, each line extending in the Y direction forms an angular irradiance distribution that is a uniform portion, but this distribution is continuously two specific at the opposite end of the illumination field 14 associated with the annular illumination setting 122 and the X dipole illumination setting 124. Changes between distributions.

Figure 22 depicts the irradiance distribution that must be generated in the field stop plane 71 by each of the overall 6x6 optical channels in this scheme. Comparing Figures 21 and 22, it can be seen that certain optical channels 136 need to produce a irradiance distribution that decreases linearly from a half maximum at the left end of the illumination field to zero at the right end of the illumination field 14. The other optical channels 138 need to produce an irradiance distribution that increases linearly from zero to the maximum irradiance level in the field stop plane 71. Further, the other optical channels 140 are required to produce an irradiance which is linearly increased from the half maximum of the left end of the illumination field 14 to the maximum value of the right end of the illumination field 14 in the field stop plane 71.

This irradiance distribution can be generated by a modulator 262 that replaces the modulator 60 of the embodiment shown in FIG. The function of the modulator 262 will be explained with reference to FIG. 23, which is the meridional direction of the three optical channels I, II and III of the optical integrator 52 and the modulator unit 260 for the optical channels I, II and III. Sectional view. In addition to the modulator unit 60 shown in FIG. 8, the modulator unit 260 shown in FIG. 23 is configured to vary the irradiance distribution within the grating field plane 58 illuminated by the beam associated with the modulator unit 260, There is no moving irradiance distribution. In other words, the light is redistributed within the illuminated area, but the position of the area does not change. In Figure 23, this is indicated by arrows A8 having different thicknesses, which indicate the irradiance at this X coordinate.

Figure 24 schematically depicts the redistribution of the spatial irradiance distribution of the three optical channels I, II and III shown in Figure 23. Likewise, it is assumed that the irradiance distribution on the inlet side of the modulator unit 260 is uniform (i.e., a top hat distribution), which is represented by a rectangle 142 in FIG. Modulator unit 260 converts rectangular irradiance distribution 142 to linearly decreasing or increasing distributions 144a, 144b, and 144c shown on the right side of FIG.

Referring again to Figure 23, the redistribution of this spatial light distribution by modulator unit 260 produces the desired irradiance distribution 136, 138, 140 in field stop plane 71 because raster field plane 58 is by third Optical grating element 56 and second concentrator 72 of array 54c are optically conjugated to field stop plane 71.

As shown schematically in FIG. 23, the uniform spatial irradiance distribution 142 is redistributed into various linearly increasing or decreasing spatial irradiance distributions that may be generated with the aid of refractive optical elements included in the modulator unit 260. In the following, it will be exemplarily described how the refractive optical element needs to be shaped to convert the uniform irradiance distribution 142 into an irradiance distribution 144b that increases linearly from zero to a maximum.

Figure 25 shows the refractive optics 146 having the front surface 148 and the back surface 149 as a point together. The shape of the front surface is assumed to be given by the equation w ₁ (x) , and the shape of the rear surface 149 is assumed to be given by the equation w ₂ (x') . It is further assumed that the light entering the front surface 148 at position x is refracted at the front surface 148 and exits the rear surface 149 at position x'.

The total light energy held in the small volume element, ie:

I ( x )d x = I' ( x' )d x' (1)

Assuming that the irradiance distribution 142 at the front surface 148 is uniform, the irradiance distribution I'(x') at the back surface 149 is:

If the irradiance distribution should increase linearly, then equation (3) must be satisfied:

Where L is the width of the illuminated area in the grating field plane 58.

Next, the equation to be solved is (with a paraxial approximation):

This set of equations can be simply understood as the light entering the refractive optics 146 at position x exits the back surface 149 at position x'. The thickness between the front surface 148 and the back surface 149 is given by w ₂ (x') - w ₁ (x) which produces an offset angle (x'-x) / (w ₂ - w ₁ ) . Next, the slope of the front surface 148 is defined by the right side of the equation dw ₁ /dx . The task of the rear surface 149 is to again change the direction of the light as it entered the front surface 148.

The helper function is:

Equation (4) can be rewritten as:

The numerical solution equation (6) produces a refractive optic 146 having the shape shown in Figure 26 on the XZ plane.

Figure 27 shows the optical component 150 contained in each of the modulator units 260 that is displaceable in the Y direction with the aid of a brake (not shown). The optical element 150 is composed of a first refractive optical member 146a and a second optical member 146b, both of which have a shape as shown in FIG. Optical element 150 is assembled from two optical members 146a, 146b, wherein optical member 146b is rotated 180° about the Z axis.

The first optical member 146a converts a uniform irradiance distribution into an irradiance distribution that linearly decreases from a maximum value to zero in the X direction, as shown by the irradiance distribution 144a on the right side of FIG. The second optic 146b redistributes the light such that the irradiance distribution obtained at its rear surface 149 increases linearly from zero to a maximum, as indicated by dashed line 144b. If the optical element 150 is displaced in the Y direction such that light is incident on both of the optics 146a, 146b, the two linearly increasing and linearly decreasing irradiance distributions 144a, 144b overlap, thereby producing a first non-zero level and A linear increase distribution 144c between the two non-zero levels, as shown in FIG.

This is shown in Figures 28 through 30, which show the front surface 140 and the brake 152 of the optics 146a, 146b in three different operating states. Brake 152 is configured to displace optical element 150 in the Y direction.

In the first operational state illustrated in Figure 28, the region 154 illuminated by the optical grating elements 56 of the first and second arrays 54a, 54b of one of the optical channels is completely located on the front surface 140 of the first optical member 146a. Inside. Therefore, the irradiance distribution 144a is generated on the rear surface 149 of the first refractive optical member 146a. Due to optical conjugation, this optical channel then produces an irradiance distribution 144a that is also on the mask plane 78.

Figure 29 shows optical element 150 in a second operational state in which region 154 is completely within front surface 140 of second refractive optic 146b. Next, the optical channel produces an irradiance distribution 144a having an opposite field dependence, i.e., it increases linearly in the -X direction.

In the third operational state illustrated in Figure 30, the optical element 150 has been moved in the Y direction such that a larger portion of one of the illumination regions 154 is within the front surface 140 of the first optic 146a and one of the illumination regions 154 is A small portion is located within the front surface 140 of the second optic 146b. Thus, an irradiance distribution 144c is obtained which is an overlap of the increased irradiance distribution 144a and the reduced irradiance distribution 144b. Thus, by means of the modulator unit 260 described with reference to Figures 23 through 30, it is possible to generate all of the irradiance distributions that have been shown in Figure 22 and that are required such that the annular illumination setting is continuously converted in the X direction of the illumination field 14 to X bipolar illumination setting.

The present invention may be embodied in other specific forms without departing from the spirit and scope of the invention. The aspects of the specific embodiments are to be considered as illustrative and not restrictive. Accordingly, the scope of the invention is indicated by the appended claims rather All changes that fall within the meaning and scope of the patent application are deemed to fall within the scope of the patent application.

10. . . Projection exposure device

12. . . Irradiation system

14. . . Field

16. . . Mask

18. . . pattern

18'. . . Reduce the image

19. . . feature

20. . . Projection objective

twenty two. . . Photosensitive layer

twenty four. . . Substrate

26. . .瞳

27. . . pole

28. . . Ring

29. . . Cover

30. . . light source

32. . . Beam expansion unit

34. . . Projected beam

36. . .瞳definition unit

38. . . Array

40. . . Micromirror

42. . . beam

44. . . beam

46. . .稜鏡

48a. . . First plane surface

48b. . . Second planar surface

49. . . Exit surface

50. . . First concentrator

52. . . Optical integrator

54a. . . First array

54b. . . Second array

54c. . . Third array

56. . . Optical grating element

58. . . Grating field plane

60. . . Modulator unit

62. . . Modulator

64. . . Control line

66. . . Control device

68. . . Central device control

70. . .瞳 plane

71. . . Field pupil plane

72. . . Second concentrator

74. . . Adjustable field diaphragm

76. . . Field light objective

78. . . Mask plane

80. . . region

81. . . region

82. . . region

83a. . . External pole

83b. . . Center pole

84. . . pole

86. . . Cylindrical lens

88. . . Cylindrical lens

90. . . Brake

92. . . Brake

94. . .稜鏡

96. . . Brake

98. . . Rotary axis

100. . . Central beam

102. . . Edge beam

104. . . Shaded area

106. . . solid line

108. . . dotted line

110. . . dotted line

112. . . Irradiation system

113. . . Triangle

113'. . . Fresnel

116. . . Optical element

118. . . Refraction wedge

120. . . Refraction wedge

122. . . Circular illumination setting

124. . . X bipolar illumination setting

126. . . region

127. . . region

128. . . Zero level

130. . . One-third irradiance level

132. . . Two-thirds irradiance level

134. . . Complete irradiance level

136. . . Optical channel

138. . . Optical channel

140. . . Optical channel

142. . . Rectangular irradiance distribution

144a. . . distributed

144b. . . distributed

144c. . . distributed

146. . . Refractive optics

146a. . . Optics

146b. . . Optics

148. . . Front surface

149. . . Back surface

150. . . Optical element

152. . . Optical integrator

152. . . Brake

154. . . region

154a. . . Array

154b. . . Array

156. . . Optical grating element

160. . . Modulator unit

162. . . Modulator

181a. . . First pattern area

181b. . . First pattern area

181c. . . First pattern area

182a. . . Second pattern area

182b. . . Second pattern area

182c. . . Second pattern area

260. . . Modulator unit

262. . . Modulator

d. . . diameter

d'. . . diameter

Fa. . . focal length

Fb. . . focal length

Fc. . . focal length

OA. . . Optical axis

I, II, III. . . Optical channel

w ₁ (x). . . equation

w ₂ (x'). . . equation

The various features and advantages of the present invention are more readily understood by reference to the Detailed Description

1 is a schematic perspective view of a projection exposure apparatus in accordance with an embodiment of the present invention;

Figure 2 is an enlarged perspective view of a mask projected by the projection exposure apparatus shown in Figure 1;

Figure 3 is a longitudinal sectional view of an illumination system, the illumination system being part of the apparatus shown in Figure 1;

Figure 4 is a perspective view of the mirror array included in the illumination system shown in Figure 3;

Figure 5 is a perspective view of an array of three optical grating elements contained in the illumination system shown in Figure 3;

Figure 6 is a plan view of an array of optical grating elements that may also be included in the illumination system of Figure 3;

Figure 7 is a cross-sectional view taken along line VII-VII of the array shown in Figure 6;

Figure 8 is a schematic longitudinal cross-sectional view of three optical channels of the optical integrator included in the illumination system of Figure 3;

Figure 9 is a top plan view of a 3x3 channel optical integrator depicting irradiance distribution in a grating field plane;

Figure 10 is a perspective view similar to the mask of Figure 2, depicting different angular irradiance distributions obtained for different pattern regions on the mask;

Figure 11 is a schematic longitudinal cross-sectional view similar to Figure 8, additionally showing the optical components within the modulator unit of Figure 8;

Figure 12 shows an alternate embodiment of a modulator unit that can be used in the embodiment shown in Figure 8;

Figure 13 is a schematic longitudinal cross-sectional view of the optical integrator of the illumination system of Figure 3, depicting the focal length of the optical grating elements included therein;

Figure 14 is a longitudinal cross-sectional view of an illumination system in accordance with another embodiment, wherein the modulator unit is disposed in a pupil plane of the illumination system;

Figure 15 is a schematic longitudinal cross-sectional view of three optical channels of the optical integrator shown in Figure 14, which is similar to Figure 8;

Figure 16 is cut from Figure 15 and shows the optical elements within the modulator unit;

Figure 17 is a cross-sectional view of a Fresnel raft in the XZ plane, which can also be used as an optical element in the modulator unit shown in Figure 16;

Figure 18 is a perspective view of yet another embodiment of an optical component included in a modulator unit comprising two wedges;

Figure 19 is a schematic illustration of an angular irradiance distribution that varies discontinuously along the X direction of the illumination field;

Figure 20 is an explanatory view showing the irradiance distribution in the grating field plane which produces the angular irradiance distribution shown in Figure 19;

Figure 21 is a schematic explanatory diagram of an angular irradiance distribution continuously changing in the X direction of the irradiation field;

Figure 22 is an explanatory diagram of spatial irradiance distribution generated by optical channels in a common field plane to produce a varying angular irradiance distribution as shown in Figure 21;

23 is a schematic longitudinal cross-sectional view of three adjacent optical channels of an illumination system that produces a continuously varying angular irradiance distribution at the mask plane;

Figure 24 is cut from Figure 23, which schematically depicts how the top-hat irradiance distribution is converted by the modulator unit to a different linearly decreasing or increased irradiance distribution;

Figure 25 is a diagram indicating the two optical surfaces of the optical member contained in the modulator unit shown in Figures 23 and 24;

Figure 26 is a diagram showing the appearance of the optical member in the XZ plane;

Figure 27 is a perspective view of an optical component comprising two optical members shown in Figure 26;

28 to 30 are front views in the Z direction of the optical element shown in Fig. 27 arranged at different X positions.

10. . . Projection exposure device

12. . . Irradiation system

14. . . Field

16. . . Mask

18. . . pattern

18'. . . Reduce the image

19. . . feature

20. . . Projection objective

twenty two. . . Photosensitive layer

twenty four. . . Substrate

OA. . . Optical axis

Claims (31)

An illumination system for a lithographic projection exposure apparatus (10) comprising: (a) an optical integrator (52; 152) comprising an array (54c; 154b) of optical grating elements (56; 156), wherein a beam profile Corresponding to each of the optical grating elements; (b) a concentrator (72) that superimposes the beams associated with the optical grating elements on a common field plane (71), the common field plane and a mask The plane (78) is identical or optically conjugated, and one of the masks (16) to be illuminated is disposed in the mask plane during operation of the illumination system (12); (c) a modulator (62; 162; 262) Is configured to adjust a field dependence of an angular irradiance distribution in an illumination field (14) that is illuminated by the illumination system (12) in the mask plane (78) and the modulation The device includes a plurality of modulator units (60; 160; 260), wherein each of the modulator units is associated with one of the beams; arranged in a position in front of the concentrator (72), Causing only the associated beam to be incident on the modulator unit (60); and configuring a spatial and/or angular irradiance distribution to variably redistribute the associated beam Without blocking any light; (d) a control device (66) configured to control the modulator units (60; 160; 260) by: if the control device receives the mask An input command of the angular irradiance distribution in the plane (78) to be adjusted, wherein at least one modulator unit redistributes the space of the associated beam and/or the angular irradiance distribution Wherein the modulator is configured such that a first angular irradiance distribution is generated from a first portion (181a, 181b, 181c) of the illumination field (14), and different from the first One of the angular irradiance distributions is generated from a second portion (182a, 182b, 182c) of the illumination field (14); and the first and second angle irradiance distributions are simultaneously produce. The illumination system of claim 1, wherein the first portion is a one-dimensional two-dimensional region (181a, 181b, 181c) in which the first-angle irradiance distribution is uniform, and wherein the second portion is the first portion The two-angle irradiance distribution is uniform one of the two-dimensional regions (182a, 182b, 182c). The illumination system of claim 1, wherein the illumination field (14) has a long dimension along one of the X directions and a short dimension along a Y direction, the Y direction being perpendicular to the X direction, and wherein the A portion (181a, 181b, 181c) has at least one Y coordinate identical to the second portion (182a, 182b, 182c), but without the same X coordinate. The illumination system of claim 1, wherein the first angular irradiance distribution and the second angular irradiance distribution are related to an illumination setting selected from the group consisting of: a conventional illumination setting, an angle illumination setting, and a double Polar illumination setting, n 4 n pole illumination setting. The illumination system of claim 1, wherein each of the modulator units (60; 260) is arranged in a grating field plane (58), the grating field plane being located in the optical grating element in a light propagation direction Prior to the array (54c), and each of the modulator units is configured to variably redistribute the spatial irradiance distribution of the correlated beam in the grating field plane without blocking any light. An illumination system according to claim 5, wherein each modulator unit (60) is configured to move in a direction perpendicular to one of the optical axes (OA) of the illumination system (12) at the grating field plane An area in (58) that is illuminated by the light beam associated with the modulator unit. The illumination system of claim 3, wherein the direction is equal to the X direction. An illumination system according to claim 6 or 7, wherein each modulator unit (60) is configured to move the illumination area without changing the angular irradiance distribution of the beam. The illumination system of claim 5, wherein the optical integrator (52) comprises a first array of optical grating elements (56), a second array, and a third calculated in a direction of light propagation. An array (54a, 54b, 54c), and wherein the grating field plane (58) is between the second array (54b) of optical grating elements (56) and the third array (54c). An illumination system according to claim 1, wherein each of the modulator units (160) is arranged in or adjacent to a plane (70), the plane of the plane being in the direction of light propagation Located after the array (154b) of optical grating elements (156), and wherein each modulator unit (160) is configured to variably redistribute the angular spread of the associated beam in the pupil plane (70) The illuminance is distributed without blocking any light. An illumination system according to claim 10, wherein each modulator unit (160) is configured to have an oblique axis perpendicular to an optical axis (OA) of the illumination system (12), the tilt being associated with the The beam of the modulator unit. The illumination system of claim 3, wherein the tilt axis is equal to the Y direction. The illumination system of claim 1, wherein each of the modulator units (60; 160; 260) comprises: (a) an optical component (86, 88; 94; 112; 112'; 116; 150), Configuring to change the direction of propagation of the associated beam incident thereon; and (b) a brake (90, 92; 96; 152) coupled to the optical component, wherein the brake is configured to receive from the response One of the control devices (66) controls the signal to change the position and/or orientation of the optical component. The illumination system of claim 13, wherein the optical element is a refractive optical element, in particular a lens (86, 88), a 稜鏡 (94; 112; 112'), in particular a Fresnel edge Mirror (112'), or a diffractive optical element. An illumination system according to claim 13 or 14, wherein the brake (90, 92; 152) is configured to displace the optical element in a direction oblique to one of the optical axes (OA) of the illumination system (12) . The illumination system of claim 13, wherein the brake (96) is configured to rotate the optical element (94) about a rotational axis (98), the rotational axis (98) being inclined to One of the illumination systems (12) is an optical axis (OA). The illumination system of claim 1, wherein the modulator (60; 160) is configured such that the angular irradiance distribution varies discontinuously over the illumination field (14). The illumination system of claim 1, wherein the modulator (260) is configured such that the angular irradiance distribution continuously varies over at least a portion of the illumination field (14). The illumination system of claim 1, wherein the first portion is a first line in which the first angle irradiance distribution is uniform, and wherein the second portion is uniform in the second angle irradiance distribution a second line, and wherein the modulator (260) is configured such that the first angular irradiance distribution is continuously converted to the region in an area disposed between the first line and the second line Second angle irradiance distribution. The illumination system of claim 19, wherein the first line is adjacent to one of the first ends of the illumination field and the second line is adjacent to one of the opposite ends of the illumination field. The illumination system of claim 20, wherein the first end and the opposite end define the illumination field along the X direction. An illumination system according to claim 18, wherein each modulator unit (260) is configured to change one of the grating field planes (58) illuminated by the light beam associated with the modulator unit An irradiance distribution within the region without shifting it. An illumination system according to claim 18, wherein each modulator unit (120) is configured to convert the irradiance distribution from a uniform irradiance distribution (142) to a linear increase or decrease along a reference direction. A irradiance distribution (144a, 144b, 144c) is modified. The illumination system of claim 23, wherein the reference direction is equal to the X direction. A method for operating a lithographic projection exposure apparatus, comprising the steps of: (a) providing a lithographic projection exposure apparatus (10) comprising an illumination system (12) and a projection objective (20); (b) providing One of the masks (16) to be illuminated by the illumination system (12); (c) defines one of the desired first angular irradiance distributions, and one of the desired second angles different from the first angular irradiance distribution An irradiance distribution; (d) obtaining the first angular irradiance distribution at a first portion (181a, 181b, 181c) of the mask and a second portion of the mask different from the first portion The portion (182a, 182b, 182c) obtains the second angular irradiance distribution to illuminate the mask (16); wherein the first portion is a one-dimensional two-dimensional region in which the first angular irradiance distribution is uniform ( 181a, 181b, 181c), and wherein the second portion is a one-dimensional two-dimensional region (182a, 182b, 182c) in which the second angular irradiance distribution is uniform. The method of claim 25, wherein the first angular irradiance distribution and the second angular irradiance distribution are related to an illumination setting selected from the group consisting of: conventional illumination setting, angle illumination setting, bipolar Illumination setting, n 4 n pole illumination setting. The method of claim 25, wherein the first portion is a first line in which the first angle irradiance distribution is uniform, and wherein the second portion is uniform in the second angle irradiance distribution. a second line, and wherein the first angular irradiance distribution is continuously converted to the second angular irradiance distribution in an area disposed between the first line and the second line. The method of claim 25, comprising controlling the first angle irradiance distribution and the second angle irradiance distribution to control one of the modulators (60, 160, 260) This step. A method of claim 25, comprising redistributing a spatial and/or angular irradiance distribution associated with a beam of optical grating elements (56; 156) contained in the illumination system without blocking any light. . The method of claim 25, wherein the mask comprises a feature pattern that is different in the first portion and in the second portion. The method of claim 25, wherein the angular irradiance distribution is changed when the mask (16) is projected from the projection objective (20) to a photosensitive surface (22) in a scanning operation.